| Constructed wetland is a valuable ecosystem, constructed wetland ecosystem is a long-term and effective purification process to achieve ecological restoration of water environment. But with the rapid development of China’s economy and society, resulting in deterioration of water environment and water pollution is getting worse. Having threaten to the security of constructed wetland ecosystem and supply water, so it is necessary to grasp the current situation and changing trend of the water quality of constructed wetland runoff and its Status to provide reference for relevant departments to take timely and effective protection measures and make scientific decision. Ensuring constructed wetland ecosystem can function normally to develop ecological restoration of water environment and guarantee the security of water supply. In this paper, the water quality of Shifosi constructed wetland is taken as the research object, using fuzzy pattern recognition method, the matter element analysis method, comprehensive water quality identification index method and water pollution index method to assess water quality. Water quality trend is analyzed with the method of seasonal Kendall test and linear regression analysis. Finally, The research results are as follows:(1) Fuzzy pattern recognition method, the matter element analysis method, water quality identification index method and water pollution index method are used to evaluate the water quality of 2009～2014 years of Shifosi constructed wetland, from the results know that:the assessment result of water pollution index method is relatively one-sided, overly pessimistic and not realistic, but this method can directly reflect the main pollutants, which is TN, TP, CODMn, NH3-N, BOD5. While results of other three methods have only a little difference, which is more comprehensive and objective.Therefore, taking the results of these three methods to measure comprehensively the water quality of shifosi constructed wetland and input water, the final evaluation result is that:input water quality of non-flood season is poor in 2009 and 2010, does not attain the third level water quality standards of water function areas, namely the water quality level of entrance section is Ⅴ or worse than Ⅴ and the water quality level of middle section is Ⅳ in 2009 non-flood. The entrance section water quality level is Ⅳ～Ⅴ, the water quality level of middle section is Ⅲ～Ⅳ in 2010 non-flood season, but when water flows through Shifosi constructed wetland, water quality level of outlet section reaches Ⅱ～Ⅲ, meet the requirement of water function area, the flood and non-flood season water quality of each section is Ⅲ or better than Ⅲ in the rest of years, showing constructed wetland has a significant purification effect to water quality.(2) Using seasonal Kendall test method and linear regression analysis method to analyze the water quality trend of 2009～2014 years of Shifosi constructed wetland, analysis results show that:seasonal Kendall test method is more accurate and objective than linear regression analysis method, therefore the result of water quality trend analysis selects seasonal Kendall test method, the results are as follows:①2009～2014, CODcr shows a high significant rise trend, TN displays a significant rise trend in Shifosi constructed wetland inlet section water, which show that water pollution characterized by CODCr and TN has become increasingly serious. Other indexes show a no obvious lift trend. Overall, the input water quality of Shifosi constructed wetland shows a deteriorating trend.②2009～2014, BOD5 shows a high significant decline trend, TP displays a significant decline trend in the middle section, which show that the organic pollution is characterized by BOD5 and TP has been controlled effectively. Other indexes show a no obvious lift trend. Overall, water quality of Shifosi constructed wetland shows a tendency to best in intermediate section, in comparison to the changes of each pollutants of incoming water, known that each pollutants of incoming water has been effectively controlled, the water quality has been further improved.(3)2009～2014, DO shows a high significant rise trend, CODMn shows a high significant decline trend and BOD5 displays a significant decline trend in outlet section, which show that the ability of oxygen recovery is enhanced, pollution characterized by CODMn and BOD5 has been controlled effectively. Overall, the water quality of outlet section displays a trend of significant improvement. With respect to inlet and intermediate section, the overall water quality has been further improved after flowing through Shifosi constructed wetland.(3) Having fully known the current situation and changing trend of the water quality of constructed wetland runoff and its Status, providing reference recommendations for protection and prevention of water environment of Shifosi constructed wetland are as follows:on the one hand, it must be to strengthen pollution source control and reduce pollutant load, on the other hand, effective measure is used to strengthen protection of Shifosi constructed wetland and improve the wastewater treatment capacity. |
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